Motor Overload Protection

SKU: C-587Duration: 24 Minutes

Pay-per-view (PPV) format perfect for individual users.

Get immediate access to this interactive eLearning course online. Must be used within 30 days, expires 48 hours after launch.

Language:  English

$19
 Add to Cart

Great for in-person classroom training or as an alternative to DVD.

Includes printable documents and Convergence Video Player for Windows systems. Content expires after 1 year.

Language:  English

$149
 Add to Cart

Great for trainers or groups who need unlimited online access to multiple courses. Available in two ways:

Motors, Drives, and Conveyors Series (Details)
Includes 17 courses for $499/year.

Industrial Maintenance Library (Details)
Includes 135 courses for $1,199/year.

Ideal for corporate licensing and high volume users.

Get Convergence courses into your current LMS to track and report employee training. Or contact us to learn more about the advantages of licensing our courses with the Convergence LMS.

Get Pricing Info

 Need help deciding? Compare delivery formats.

Course Details

Specs

Training Time: 24 minutes

Compatibility: Desktop, Tablet, Phone

Based on: Industry Standards and Best Practices

Languages: English

Large alternating current motors are vital to modern life and industry. While motors are relatively simple devices, they can be installed or operated incorrectly or develop operational problems. For protection of the motor and for safety reasons, electrical motors require protective devices on their power supply systems. Circuit breakers and fuses are used to provide protection from very high-current short circuits and ground faults. Overload devices are used to protect from longer period, moderate overcurrent events. This module will focus primarily on the role and function of the overload protection devices.

Learning Objectives

At the end of this module, you will be able to:

  • Describe the purpose of fuses and circuit breakers
  • Differentiate between a short circuit fault and an overload
  • Explain the principles of operation behind thermal overload devices
  • List some causes for motor overload
  • Explain the principle of operation behind magnetic overload devices
  • Explain the principle of operation behind electronic overload devices
  • Describe the NEMA trip class numbering system

Key Questions

The following key questions are answered in this module:

What is the difference between circuit breakers and overload protection devices?
Circuit breakers operate by stopping power in very high overcurrent situations such as those that would occur from a short circuit or a ground fault. An overload protection device is meant to protect a motor from operating for prolonged periods of time at a current that is moderately above full load amperage.

What are some conditions that can lead to motor overloading?
Motor overloading can be caused by an increase in the load being driven by the motor, bearing failure in the motor or the driven load, or an electrical problem such as a low input voltage or single phasing.

How does a bimetallic overload device work?
Bimetallic strips bend when heated. In an overload device, a small heater is wired in series with a motor winding. If excessive current flows through the heater, it causes the strip to bend sufficiently to open the contacts that supply power to the motor winding.

What role do current transformers play in overload protection?
Current transformers are sensors that surround a power conductor line. By electrical inductance, the flow of current in the transformer is proportional to the flow in the primary conductor. The reduced current in the transformer circuit permits the use of smaller overload devices.

What does the NEMA trip class of an overload device indicate about the device?
The NEMA trip class is the number of seconds required for the overload device to trip at a current of 600% of the full load amperage of a motor.

Sample Video Transcript

Below is a transcript of the video sample provided for this module:

There are several types of overload devices which can be placed in line with a motor winding to prevent damage from overheating. Two types of devices rely on a thermal element for protection. The first uses a bimetallic strip. A bimetallic strip consists of two strips of metal bonded together. As the temperature of the strip increases, the metals expand at different rates, causing the strip to bend. This bending upon heating can be used to make or break contacts in an overload device. In the diagram shown, an electric heater in series with the winding of a motor generates heat in proportion to the current flowing through the motor. If the current increases, the heater generates more heat, the bimetallic strip bends and opens the contacts which trips out (or stops) the motor.

Additional Resources

Use the additional resources and links below to learn more about this topic:

Customer Q&A

I would like to have several employees take multiple courses. How can I set that up?

We're in the process of making bulk course and multiple user purchases easier. But for now, you can order multiple courses and contact us with details on who you'd like to assign courses to. We can set up each user's training plan and make sure everyone gets the eLearning assignments they need.

Can I get a free full-length preview of a course to see what this course covers?

While we do our best to offer details on course contents, we don't normally offer full-length previews. But please contact us with more details for a better understanding of what your organizaton needs and how we can help.

Do I get a certificate when I complete a course?

Yes. All of our courses allow you to print a completion certficate upon successfully passing the integrated test at the end of each eLearning course.

How do I log in to take a course that I have already paid for?

You'll receive an email with login details moments after you purchase your pay-per-view (PPV) course. Just click the login link and enter the user name and password provided.

Do you have courses in different languages?

Yes. While all of our courses are originally produced in English, we develop many courses in a growing number of languages, including Chinese, Dutch, German, Italian, Japanese, Korean, Polish, Portuguese, Russian, Spanish, Tamil, and Thai. Available languages are normally displayed in the Course Details section on each course page.
Added to Cart! Click here to view your cart.
Training Software
eLearning Courses
Solutions
Convergence Training Newsletter

Stay up to date on our products and offerings and get safety, compliance, and training administration tips in our free monthly newsletter.

© Convergence Training | Privacy Policy